1. Field of the Invention
The present invention relates to a fuel cell, and more particularly, to a power controlling apparatus for a fuel cell system capable of stably maintaining an outputtable power from a fuel cell system by performing a communication between a fuel cell controlling unit and a power conversion controlling unit, and a method thereof.
2. Description of the Background Art
Generally, a fuel cell system converts energy from a fuel cell into electric energy.
In a fuel cell, an anode and a cathode are formed at both sides of a high molecule electrolyte. An electrochemical oxidation of hydrogen, which is a fuel, is generated at the anode, and an electrochemical deoxidation of oxygen, which is an oxidizer, is generated at the cathode.
Electrons are generated by the electrochemical oxidation and the electrochemical deoxidation, and electric energy is generated as the generated electrons move in the fuel cell.
There are several types of fuel cells, such as, for example, a Phosphoric Acid Fuel Cell (PAFC), an Alkaline Fuel Cell (AFC), a Proton Exchange Membrane Cell (PEMFC), a Molten Carbonate Fuel Cell (MCFC), a Solid Oxide Fuel Cell (SOFC), and a Direct Methanol Fuel Cell (DMFC).
Applications of fuel cells include commercial fuel cells, home fuel cells, vehicle fuel cells which power electric motors, and small fuel cells which power portable terminals, notebooks, etc.
Home fuel cells are being developed which can power electric appliances, lighting systems and the like, and commercial fuel cells are being developed which can power lighting devices, motors, machines and the like which are used in a building, a factory, etc.
A fuel cell system interacts with a power supply system (such as, for example, an electric utility). When the amount of power the fuel cell system supplies to a load is deficient, the deficient amount is compensated for by the power supply system. On the contrary, when the amount of power the fuel cell system supplies to a load is in excess, the excess amount is supplied to the power supply system.
FIG. 1 is a block diagram showing a construction of a conventional power supply apparatus for a fuel cell system.
As shown, the power supply apparatus for the fuel cell system includes a fuel cell 1, a power converting unit 2, and a power supplying unit 3.
The fuel cell 1 includes a stack (not shown) which generates electricity by an electrochemical reaction between hydrogen and oxygen at a cathode and an anode. A DC voltage is generated from the stack.
The power converting unit 2 includes a DC/DC converting unit and an inverter (both not shown). The DC/DC converting unit converts the DC voltage generated by the stack into an AC voltage, boosts or lowers the converted AC voltage, and then outputs a DC voltage after rectifying the boosted or lowered AC voltage. The inverter converts a DC voltage outputted from the DC/DC converting unit (not shown) into an AC voltage.
The power supplying unit 3 supplies power to a home or other building, and may be, for example, an electric utility generation plant.
In the fuel cell system, information exchange is not performed between an entire controlling unit for performing an entire control and a power controlling unit for controlling a power output from the fuel cell. Accordingly, a power amount more than an outputtable amount from the fuel cell system is outputted by the power controlling unit, and a voltage of the fuel cell system is drastically lowered, which is called as a voltage dip phenomenon. Accordingly, stability of the fuel cell system is lowered, and a lifespan of the fuel cell system is shortened due to a large load applied to the stack.